/*      $NetBSD: pthread_barrier.c,v 1.23 2022/02/12 14:59:32 riastradh Exp $   */

/*-
 * Copyright (c) 2001, 2003, 2006, 2007, 2009, 2020 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Nathan J. Williams, by Jason R. Thorpe, and by Andrew Doran.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__RCSID("$NetBSD: pthread_barrier.c,v 1.23 2022/02/12 14:59:32 riastradh Exp $");

/* Need to use libc-private names for atomic operations. */
#include "../../common/lib/libc/atomic/atomic_op_namespace.h"

#include <errno.h>

#include "pthread.h"
#include "pthread_int.h"

int
pthread_barrier_init(pthread_barrier_t *barrier,
                     const pthread_barrierattr_t *attr, unsigned int count)
{

        pthread__error(EINVAL, "Invalid barrier attribute",
            attr == NULL || attr->ptba_magic == _PT_BARRIERATTR_MAGIC);
        if (count == 0)
                return EINVAL;

        barrier->ptb_magic = _PT_BARRIER_MAGIC;
        PTQ_INIT(&barrier->ptb_waiters);
        barrier->ptb_initcount = count;
        barrier->ptb_curcount = 0;
        barrier->ptb_generation = 0;
        return 0;
}

int
pthread_barrier_destroy(pthread_barrier_t *barrier)
{

        pthread__error(EINVAL, "Invalid barrier",
            barrier->ptb_magic == _PT_BARRIER_MAGIC);
        if (barrier->ptb_curcount != 0)
                return EBUSY;

        barrier->ptb_magic = _PT_BARRIER_DEAD;

        return 0;
}

int
pthread_barrier_wait(pthread_barrier_t *barrier)
{
        pthread_mutex_t *interlock;
        pthread_t self;
        unsigned int gen;

        pthread__error(EINVAL, "Invalid barrier",
            barrier->ptb_magic == _PT_BARRIER_MAGIC);

        /*
         * A single arbitrary thread is supposed to return
         * PTHREAD_BARRIER_SERIAL_THREAD, and everone else
         * is supposed to return 0.  Since pthread_barrier_wait()
         * is not a cancellation point, this is trivial; we
         * simply elect that the thread that causes the barrier
         * to be satisfied gets the special return value.  Note
         * that this final thread does not actually need to block,
         * but instead is responsible for waking everyone else up.
         */
        self = pthread__self();
        interlock = pthread__hashlock(barrier);
        pthread_mutex_lock(interlock);
        if (barrier->ptb_curcount + 1 == barrier->ptb_initcount) {
                barrier->ptb_generation++;
                barrier->ptb_curcount = 0;
                pthread__unpark_all(&barrier->ptb_waiters, self,
                    interlock);
                pthread_mutex_unlock(interlock);
                return PTHREAD_BARRIER_SERIAL_THREAD;
        }
        barrier->ptb_curcount++;
        gen = barrier->ptb_generation;
        for (;;) {
                PTQ_INSERT_TAIL(&barrier->ptb_waiters, self, pt_sleep);
                self->pt_sleepobj = &barrier->ptb_waiters;
                (void)pthread__park(self, interlock, &barrier->ptb_waiters,
                    NULL, 0);
                if (__predict_true(gen != barrier->ptb_generation)) {
                        break;
                }
                pthread_mutex_lock(interlock);
                if (gen != barrier->ptb_generation) {
                        pthread_mutex_unlock(interlock);
                        break;
                }
        }

        return 0;
}

#ifdef _PTHREAD_PSHARED
int
pthread_barrierattr_getpshared(const pthread_barrierattr_t * __restrict attr,
    int * __restrict pshared)
{

        pthread__error(EINVAL, "Invalid barrier attribute",
            attr->ptba_magic == _PT_BARRIERATTR_MAGIC);

        *pshared = PTHREAD_PROCESS_PRIVATE;
        return 0;
}

int
pthread_barrierattr_setpshared(pthread_barrierattr_t *attr, int pshared)
{

        pthread__error(EINVAL, "Invalid barrier attribute",
            attr->ptba_magic == _PT_BARRIERATTR_MAGIC);

        switch(pshared) {
        case PTHREAD_PROCESS_PRIVATE:
                return 0;
        case PTHREAD_PROCESS_SHARED:
                return ENOSYS;
        }
        return EINVAL;
}
#endif

int
pthread_barrierattr_init(pthread_barrierattr_t *attr)
{

        attr->ptba_magic = _PT_BARRIERATTR_MAGIC;
        return 0;
}

int
pthread_barrierattr_destroy(pthread_barrierattr_t *attr)
{

        pthread__error(EINVAL, "Invalid barrier attribute",
            attr->ptba_magic == _PT_BARRIERATTR_MAGIC);
        attr->ptba_magic = _PT_BARRIERATTR_DEAD;
        return 0;
}